华北某些地区石炭—二叠系成岩作用及成岩阶段的研究

成岩作用及成岩阶段的确定是储集层评价的重要依据。作者应用铸体薄片、阴极发光、扫描电镜的观察,x射线衍射分析及包体测温等方法,对华北一些地区石炭一二叠系砂岩的成岩作用及成岩阶段作了系统的研究。从太原组到上石盒子组,由于沉积环境、岩石类型的差异,它们经历了不同的成岩作用过程。太原组石英砂岩以石英增生与胶结作用为主;山西组长石砂岩及长石石英砂岩以长石及石英增生、碳酸盐胶结交代作用为主;上、下石盒子组粘土含量较高的岩屑砂岩以压实作用、粘土矿物的转化作用为主。 成岩阶段的确定主要根据自生石英中包裹体测温、镜煤反射率测定及粘土矿物的演变等。研究结果得出石炭一二叠系经历的古地温为100—150℃,有机质处于成熟期,粘土矿物转化为以伊利石为主,混层矿物中伊利石达80％,可见研究区内石炭一二叠系的成岩阶段处于中成岩期的晚期。其原始孔隙基本消失,代之以一定次生孔隙。

DIAGENESIS AND DIAGENETIC STAGE OF PERMOCARBONIFEROUS IN SOME AREAS OF NORTH CHINA

Diagenesis of Permo-Carboniferous of North China constitutes one important aspect of oil and gas reservoir evaluation. With the help of some newly-established experimental facilities in sedimentology, we studied the diagenetic processes that have significantly altered Permo-Carboniferous sandstones. From Taiyuan Formation upwards to Upper Shihezi Formation, sedimentary environments and fades have evident influence on diagenesis.Quartz cementation characterizes the sandstones of Taiyuan Formation,causing the lose of primary pores. Cathodoluminescence and clay mineral data reveal the source of silica to be more the transformation of clay minerals in shales than pressure solution. Diagcnesis in sandstones of Shanxi Formation is characterizd by aboundant feldspar overgrowth and quartz overgrowth. Authi-genic feldspars arc exclusively potassium feldspar. In sandstones of Lower and Upper Shihezi Formation the dominating diagenetic processes are mechanical compaction and clay matrix transformation. Microthermometric examination of fluid inclusions in quartz cement, together with vitrinite reflectivity and clay mineral assemblage analysis, indicates that the top temperature that occured in Permo-Carboniferous strata ranges from 100 to 150 . The diagenetic stage, as indicated by top temperature and petrographic evidence, is classified into late middle diagc-nesis, when rocks have undergone relatively strong diagenetic modifications and primary pores are substituted by secondary pores.